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Old 20th December 2004, 12:53 PM   #21
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I'm just trying not to force feed people, as I know it's annoying.
That depends heavily on the taste of the food.

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$200 - $300
At the current exchange-rate for the USD this would be an interesting price for 2 channels + PSU + signal processing (can you implement transient-perfect crossovers as well ?).

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It's not trademarked in the UK and I haven't had a writ from Mr Gates.
I assume he would actually be pleased if you caused confusion with the other ".....-pod".

Regards

Charles
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Old 20th December 2004, 07:15 PM   #22
davey1 is offline davey1  United Kingdom
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Hi Charles

Not actually quoting prices for the unit, just an example to illustrate the issue.

What do you mean by 'phase perfect' - FIR filters?

Thanks,

Davey
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Old 20th December 2004, 08:12 PM   #23
davey1 is offline davey1  United Kingdom
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Oops!

Meant, 'transient perfect'
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Old 21st December 2004, 06:26 AM   #24
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Hi Davey

Yes, that could be one solution. But there would also be possibilities for transient perfect IIR filters.
A possible candidate is a proposal by John Kreskovsky (a sporadic poster on this forum). He subtracts a lowpass with constant group delay (i.e. Bessel) from a constant delay (i.e. a simple circular buffer) to obtain the highpass. The summed response is exactly representing the input in time- and frequency- domain.
The advantage over a FIR crossover is that it doesn't have pre-ringing. The disadvantage is its asymmetric slopes.

Regards

Charles
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Old 14th January 2005, 03:33 PM   #25
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Default Re: Re: Best Sounding Class D Amp

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Originally posted by sven-ake
Zappulse from LC Audio should be something to try you can build them very powerful if you like.I have mine driving martin Logan SL3 and it works really good and they are very easy to build.With the PSU i use they can deliver approx.700w in 4 ohms
Another newbie to this forum. I read the info on the LC Audio website and it seems reasonably easy for someone slightly hamfisted (myself) to build a working amplifier. Add a decent sized transformer.....

But the real question is, how good is the sound from the ZAPPulse? I don't have any unused >1KVA traffos on the shelf so every nut and bolt has to be purchased for this project. Therefore I would like to know what to expect. The last sentence should read: what you found when you built your amplifier. Sound quality is a very subjective thing, but how does it compare to commercially available amplifiers? In round figures I reckon on a spend of 750.00 so is it reasonable to compare a self built amplifer with a commercially built unit retailing at 1.5K? Thanks for taking the time to read this post, hope my query makes sense.
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Old 14th January 2005, 08:02 PM   #26
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Hi,

The zappulse 2.2 SE is a very good sounding module but I think this strongly depends on the speaker you want to drive with it. The experiences with speaker with complex impedances are not so good aparantly. Low impedance is no problem at all the modules can deliver lot's of current

I've had experience with Zap and Ice and the Zap sounds better than Ice IMHO, and the zap also sounds better than a Krell KSA 100 MK2. They outperformed the Rotel RB980BX by a very large margin.
I never heard the UCD modules.
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Old 15th January 2005, 11:08 PM   #27
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Default zappulse drive capability

Eric's answer is similar to my experiences- I have M-L Ascents [v. difficult load], and with the PSU on the upper end of the recommended voltage rail I had some early rolloff of LF. This was not the case with the UCD modules.

I saw mentioned in the forum recently that you reduce the output impedance of the Zaps by lowering their rail volts, so that's next to try.
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Old 18th January 2005, 07:31 PM   #28
GregD is offline GregD  United States
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I've experimented a bit with 2.2SE Zappulse and have found it to sound very good with a beefy power supply. I have a pair of Watt/Puppy 6s and my normal amp is a Threshold S/500 II which I've been very happy with over the years. My comments below are in comparison to the Threshold.

I tried LC Audio's Predator power supply with two modules side by side, and found the channel separation to be poor, the bass had an initial impact but no body, and a rather closed in sound like the high frequencies were rolled off.

Then I tried paralleling some big capacitors (84,000uf) with the Predator power supply. This dramatically improved the bass and suprisingly enough helped the highs quite a bit as well. The channel separation was still bad and the highs still sounded rolled off, but not as bad as before.

So I decided to try a totally maxed out power supply with separate monoblocks. Each amp has a 1500VA transformer with 328,000uf of capacitors with bridge rectifiers and some bypass capacitors. With this combination, the amp was finally a contender; separation was excellent (as you would expect), the impact, dynamics, and control were outstanding and superior to the Threshold. The sound is very clean with excellent clarity and a great soundstage, but the highs still seem a bit rolled off; there's not the same airy spaciousness to the sound I get with the Threshold. Also, at medium to high volume levels the midrange gets a recessed sound, almost like it's at the end of a long tube, kind of a weird effect that is hard to describe.

I plan on trying a little RC snubber on the main caps with a 100uf cap attached directly to the modules like the chip amp folks have been discussing to see if this will make any difference to the sound. Also, I really want to try some of the UCD modules when they start making them again; hopefully they'll do the nice things the Zaps do without the odd things.

In summary, there's a number of things I like about the Zappulse amps better than the Threshold including having a generally clearer and less distorted sound, but the weird recessed sound effect and the less open sounding top end have me sticking with the Threshold. But they sound better than a couple of other amps I've tried in my system, an Adcom GFA-555 and a Cary Audio CAD572SE, and I think better than many other amps that I've tried in other systems over the years.

Just my observations and opinions. YMMV!
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Old 19th January 2005, 12:09 AM   #29
GregD is offline GregD  United States
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Default Pictures of Zappulse test amp

Here's a picture of the test amp configuration I put together. I had a couple of old computer cases laying around, so they were pressed into service for experimental purposes, some modification required.
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Old 19th January 2005, 12:25 AM   #30
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Greg, thanks for your informative comment. Interesting how that particular amp came together for you using the mondo-supply approach. I wonder if a judicious use of film capacitors might help in the airiness department? But might also augment certain of the weird effects of which you speak?

Cheers.
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